<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		
		<script>
			var a =1;
			var b=--a;
			console.log('a='+a);
			console.log('b='+b);
			
			var aa = 5;
			var bb = 10;
			console.log(aa+bb);
			
			var cc = '5';
			var dd = '10';
			console.log(cc+dd);  //15 510
			
			/**
			 * ==   表示只要值相等就行。类型不需要相等
			 * ===  不仅值要相等  而且类型也要相等
			 */
			
			console.log('aa == cc '+(aa == cc));   //等于      true
			console.log('aa === cc '+(aa === cc)); //恒等于  false
			
			var ccc = parseInt(cc);
			
			console.log('aa === ccc '+(aa === ccc)); //恒等于  true
			var ddd = parseInt(dd);
			console.log(ccc+ddd);  //15
		</script>
	</body>
</html>
